The present invention relates to a device for a continuous introduction of bulk material into a pneumatic conveyer line and particularly relates to a pneumatic bulk transfer device having an intermittently fed transfer vessel that intermittently feeds a dispensing vessel.
The present invention is intended to be used in areas where there is a height limitation which restricts the maximum height of a material transferring dispensing device. Many conventional devices distribute or dispense particulate material, such as sand and cement, from a dispensing vessel under the influence of gravity. Where the flow of the dispensed material is metered, it is conventional to use a series of stacked vessels. The lowermost vessel is a dispensing vessel from which the material is dispensed in metered quantities. The uppermost vessel or vessels are transfer and supply vessels from which material is transferred into the dispensing vessel. This arrangement results in a structure which is quite tall and requires extensive headroom on site. Where sufficient headroom is not available other structure must be used, for example, a conventional structure places a supply or transfer vessel apart from a dispensing vessel and transfers material from the transfer vessel to the dispensing vessel using screw conveyers, airlifts or pneumatic conveyers and similar equipment. U.S. Pat. No. 3,844,446 illustrates a conventional arrangement.
Many conventional methods have the disadvantage of requiring high power consumption for moving parts, or of having high wear rates of moving parts or pneumatic tubing or require quantities of high pressure air at several pressures, as is not normally available on a site of this type. Conventional methods using blow tanks, for example, usually require multiple blow tanks to achieve enough throughput to supply the dispensing vessel for continuous dispensing or limit the output of the dispensing vessel. Transfer from a blow tank is semi-batch in nature; transfer must stop to permit the blow tank to accumulate sufficient material to supply the dispensing vessel.
Applicants have devised a method and apparatus for supplying a dispensing vessel that will continuously dispense and meter large quantities of pulverized or granular material, and applicant's apparatus is small in height compared to conventional stacked transfer devices. A transfer vessel of the present invention is capable of feeding a dispensing vessel from a remote location and both vessels use one source of pressurized fluid, typically pressurized air, for transferring, fluidizing, metering and dispensing the material. The one source, however, is utilized to provide multiple pressure outputs. For example, orifice plates can be used to provide different pressure feeds to the components in applicant's system.
In accordance with one embodiment of the present invention a transfer vessel is operated intermittently to feed a dispensing vessel and obtain continuous output from the dispensing vessel. The transfer vessel need not be large, but can be cycled sufficiently rapidly to maintain the dispensing vessel with a continuous output. Applicant's method and device dispenses uniform quantities of almost any pulverized or granular material, for example, sand, cement, powdered plastic resins and other materials having a wide range of densities. The throughput through applicant's equipment is produced by a low to moderate pressure differential and at sufficiently low linear velocity that the wear on the material is not excessive. Applicant's structure can be used to replace existing units and can fit in cramped quarters. The device does not require excessive headroom. Applicant's device permits the transfer vessel to be separated from the dispensing vessel in a wide variety of configurations to accommodate the available site configuration. This has the advantage of permitting the equipment to be installed in a variety of locations currently existing without the requirement for expensive remodeling of the site or new site construction.
It is thus an object of the applicant's invention to provide a conveying and dispensing system which is effective to handle substantially all pulverized and granular material.
It is a further object of applicant's invention to provide a dispensing and conveying system which transfers material from a transfer vessel spaced apart from a dispensing vessel.
It is a further object of applicant's invention to provide a conveying and dispensing system which can operate to continuously dispense material while intermittently transferring material from a small transfer vessel to a larger dispensing vessel.
It is a further object of applicant's invention to provide a conveying and dispensing system which can use air from one pressure source for fluidizing, transferring and metering material.
It is a further object of applicant's invention to balance the pressure as required in applicant's system by using orifices to maintain the pressure drop within the components of the system at the needed levels.